The present invention relates to the sealing device utilized for a construction machine, a vehicle for civil construction engineering or an engine of an automobile and, more particularly, to a sealing device provided with a seal lip made of resin material and a seal lip made of rubber-like elastic material, which are firmly sealingly engaged with each other, and also relates to a method of manufacturing the sealing device.
One example of conventional sealing devices will be described hereunder with reference to FIGS. 10 and 11.
Referring to FIG. 10, a sealing device is generally designated by reference numeral 100. The sealing device 100 comprises a first seal ring 103 provided with a seal lip 102 made of resin (hereinafter resin seal lip 102) hermetically contacting a rotating shaft 101 of a machinery such as a construction machine to which the sealing device is applied, and a second seal ring 105 provided with a seal lip 104 made of rubber-like elastic material (hereinafter rubber seal lip 104). These two seal rings 103 and 105 are in a tightly contacting relationship, but not bonded to each other. To the second seal ring is bonded a reinforcing ring 106 which are formed a plurality of holes 107 on the circumferential portion thereof. The first seal ring 103 is provided with a base portion 108 on which are formed a plurality of projections 108a, which are engaged with the holes 107 of the reinforcing ring 106, for preventing the first seal ring from being rotated. An annular seal member 109 made of a felt material is disposed on one side, i.e., atmosphere side A of the second seal ring 105.
Before the application of the sealing device 100 to a housing 110 to be sealed, the inner diameter of the rubber seal lip 104 is made smaller than the outer diameter of the rotation shaft 101 in a state shown by a dotted line in FIG. 10 for ensuring an interference fit, and the back surface opposite the sealing surface by, of the resin lip 102 is in close contact with the second seal ring 105. When the second seal ring 105 is mounted, the rubber lip 104 is deformed as shown by a white arrow to thereby form a gap d between the back surface of the resin lip 102 of the first seal ring 103 and the second seal ring 105. An annular groove 111 is formed in the sealing surface of the resin lip 102.
In the sealing device 100 of the structure described above, the atmosphere on the side A in FIG. 10 is sucked through the grooves 111 by pumping action during the rotation of the rotating shaft 101 and the sealing fluid B is thus sealed. When the shaft 101 is not rotated, the sealing fluid B is sealed by the rubber lip 104. During the described operation of the sealing device 100, once the first and second seal rings 103 and 105, as well as the first seal ring 103 and the reinforcing ring 106, are not connected, the resin lip 102 and the rubber lip 104 of the first and second seal rings 103 and 105 are not influenced by each other, thus performing the sealing function.
In general, the sealing device of the structure described above may be formed in a formation mold, not shown, by heat compressing the first seal ring 103 and rubber material and then carrying out the vulcanization treatment to thereby tightly secure the both materials with relatively low cost.
However, with the sealing device 100 shown in FIG. 10, in a case where the sealing fluid B leaks on the side of the resin lip 102 by the lowering of the sealing performance due to the wearing or degradation of the rubber lip 104, the leaking fluid leaks on the side of the atmosphere A through the gap b, as shown by black arrows, between the contacting surface of the second seal ring 105 and the base portion 108 of the first seal ring 103 and the contacting surface of the base portion 108 and the reinforcing ring 106.
In another example of a sealing device 200 shown in FIG. 11, the first seal ring 202 provided with a resin lip 201 and the second seal ring 204 provided with a rubber lip 203 are formed independently and, thereafter, the sealing device 200 is formed by caulking, as shown by a symbol R in FIG. 11, the outer periphery of a reinforcing ring 205 integrally formed with the second seal ring 204.
According to this example, the leakage of the sealing fluid caused in the aforementioned example is not caused because of the formation of the caulked portion. However, it is obliged to additionally dispose a reinforcing ring 206 for supporting the first ring 202 and, in addition, the caulking process is required for assembling the first seal ring 202 and the second seal ring 204, thus increasing the manufacturing process and cost.
In a further example of the sealing device shown in FIG. 12, the sealing device 300 comprises a second seal ring 301 and a first seal ring 302 closely contacting to the second ring 301 on the side of the atmosphere A. The second seal ring 301 includes a sealing body composed of an annular engaging portion 303, a flanged portion 304 and a rubber seal lip 305 axially extending towards the sealing fluid side B and a metal ring 306. The first seal ring 302 includes a flanged portion 307 extending in a direction of the diameter of the rotation shaft and a resin seal lip 309 provided with a thread groove 308.
In the sealing device 300 of the structure described above, the rubber seal lip 305 and the resin seal lip are in close contact before the mounting thereof as shown in solid outline in FIG. 12, but when both the seal lips are assembled in a portion between the housing 310 and the rotation shaft 311, the seal lips 305 and 309 are elastically deformed in the diameter direction by amounts different from each other as shown by the dot and dash line (in the illustration, only the deformation amount of the seal lip 305 is shown), thereby achieving the sealing performance therebetween. Accordingly, the first and second seal rings 302 and 301 are in the state merely in contact with each other and the projection 313 formed to a sealing body S is engaged with an engaging hole 312 formed to the flanged portion 307 of the first seal ring 302 to thereby attain the rotation prevention function between the respective seal rings 301 and 302.
FIG. 13 shows a still further example of the sealing device of the prior art and the sealing device 400 is of substantially the identical structure of the sealing device 300 shown in FIG. 12 except as described below.
In the sealing device 400, an engaging hole 414 is formed in a metal ring 406, and an engaging projection 415 formed to a second seal ring 402 is engaged with the hole 414 to thereby attain the rotation prevention function between the first and second seal rings.
The other structures and the description thereof are eliminated herein by increasing the reference numerals herein by 100 in FIG. 13 to that applied to portions or members corresponding to those shown in FIG. 12, for example, second seal ring 301 in FIG. 12 is increased in number to arrive at second seal ring 401 in FIG. 13.
In both the examples shown in FIGS. 12 and 13, the sealing device 300 or 400 attains the sealing function for the sealing fluid B by sucking the atmosphere on the side A of the atmosphere by pumping function through the thread groove 308 or 408 during the rotation of the rotation shaft 311 or 411. When the rotation of the rotation shaft stops, the sealing of the fluid B can be performed by the seal lip 305 or 405. The sealing devices 300 or 400 are usually formed by a vulcanization treatment in a closely contacting condition with a desired shape by heating and pressing the ring-shaped resin material, metal ring and rubber material in a cavity of a mold, not shown.
However, with the sealing device 300 or 400 shown in FIGS. 12 or 13, in a case where the sealing fluid B leaks on the side of the resin lip 309 or 409 by the lowering of the sealing performance due to the wearing or degradation of the rubber lip 305 or 405, the leaking fluid leaks on the side of the atmosphere A through the gap d and the engaging hold 312 and through the contacting surface of the first seal ring 302 and the metal ring 306 (FIG. 12), and through the outer peripheral side of the first seal ring 402 and the engaging hole 414 (FIG. 13).
In addition, according to these examples, it is necessary to form the first seal ring before the vulcanization treatment so as to have an L-shaped cross section at the manufacturing of the sealing device. Furthermore, the engaging hold 312 of the first seal ring 302 and the engaging hole 414 of the metal ring 406 are additionally required for the manufacture of the sealing devices 300 or 400, thus being troublesome and involving increased manufacturing cost.